U.S. patent number 11,446,486 [Application Number 17/337,944] was granted by the patent office on 2022-09-20 for multielectrode medical lead.
The grantee listed for this patent is Gopi Dandamudi, Terrell M. Williams. Invention is credited to Gopi Dandamudi, Terrell M. Williams.
United States Patent |
11,446,486 |
Dandamudi , et al. |
September 20, 2022 |
Multielectrode medical lead
Abstract
A medical lead includes a lead body, a proximal connector, a
helix extending from a distal end of the lead body. The helix is
configured to anchor to a patient tissue, and the helix forms a
helical electrode. The medical lead further includes a distal ring
electrode, and a cable within the lead body, the cable including a
cable conductor, a cable electrode proximate a distal end of the
cable conductor, and a blunt dissection tip at a distal end of the
cable. The cable is slidable within the lead body to extend and
retract the cable electrode along a trajectory extending from the
distal end of the lead body. When the helix is anchored to the
patient tissue, the blunt dissection tip is configured to blunt
dissect the patient tissue along the trajectory extending from the
distal end of the lead body through extension of the cable.
Inventors: |
Dandamudi; Gopi (Gig Harbor,
WA), Williams; Terrell M. (Brooklyn Park, MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Dandamudi; Gopi
Williams; Terrell M. |
Gig Harbor
Brooklyn Park |
WA
MN |
US
US |
|
|
Family
ID: |
1000005649605 |
Appl.
No.: |
17/337,944 |
Filed: |
June 3, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N
1/37512 (20170801); A61N 1/362 (20130101); A61N
1/0573 (20130101); A61N 2001/058 (20130101) |
Current International
Class: |
A61N
1/05 (20060101); A61N 1/375 (20060101); A61N
1/362 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Kawashima et al., A macroscopic anatomical investigation of
atrioventricular bundle locational variation relative to the
membranous part of the ventricular septum in elderly human hearts,
Surgical & Radiologic Anatomy, Feb. 19, 2005, pp. 206-213, vol.
27, Springer-Verlag, Heidelberg, Germany. cited by applicant .
Medtronic, C315 Catheter: For the SelectSecure.RTM. Pacing lead
system, Dec. 2008, Medtronic, Inc., Minneapolis, Minnesota. cited
by applicant .
Medtronic, HIS--Bundle Pacing Introductory Tutorial, May 2017,
Medtronic, Inc., Minneapolis, Minnesota. cited by applicant .
Abdelrahman et al., Clinical Outcomes of His Bundle Pacing Compared
to Right Ventricular Pacing, JACC vol. 71, No. 20, May 22, 2018,
pp. 2319-2330, The American College of Cardiology Foundation,
Washington, DC. cited by applicant .
Vijayaraman et al., Prospective evaluation of feasibility and
electrophysiologic and echocardiographic characteristics of left
bundle branch area pacing, Heart Rhythm vol. 16, No. 12, Dec. 2019,
pp. 1774-1782, Heart Rhythm Society, Washington, DC. cited by
applicant .
Williams et al., Cardiac Pacing Lead, Lund IP Docket No.
1004-001US01, U.S. Appl. No. 16/826,007, filed Mar. 20, 2020. cited
by applicant.
|
Primary Examiner: Bertram; Eric D.
Attorney, Agent or Firm: Lund IP, PLLC
Claims
The invention claimed is:
1. A medical lead comprising: a lead body; a connector proximate to
a proximal end of the lead body; a helix extending from a distal
end of the lead body, wherein the helix is configured to anchor to
a patient tissue, and wherein the helix forms a helical electrode;
a ring electrode proximate to the distal end of the lead body; and
a cable within the lead body, the cable including a cable
conductor, a cable electrode proximate a distal end of the cable
conductor, and a blunt dissection tip at a distal end of the cable,
wherein the cable conductor is a solid wire or a stranded wire,
wherein the cable is slidable within the lead body to drive
extension and retraction of the cable electrode along a trajectory
extending from the distal end of the lead body, and wherein, when
the helix is anchored to the patient tissue, the blunt dissection
tip is configured to blunt dissect the patient tissue along the
trajectory extending from the distal end of the lead body and past
a distal end of the helix through extension of the cable.
2. The medical lead of claim 1, wherein the cable is slidable
within the lead body to extend the cable electrode at least 1.8
centimeters from the distal end of the lead body.
3. The medical lead of claim 1, further comprising: a first
conductor within the lead body connecting the helical electrode to
a first electrode of the connector; and a second conductor within
the lead body connecting the ring electrode to a second electrode
of the connector, wherein the cable conductor connects the cable
electrode to a third electrode of the connector.
4. The medical lead of claim 3, wherein the third electrode is a
connector pin.
5. The medical lead of claim 3, wherein the blunt dissection tip is
a hemispherical tip.
6. The medical lead of claim 1, wherein the blunt dissection tip
forms a rounded frontal surface extending across a width of the
cable.
7. The medical lead of claim 1, wherein the cable electrode has a
diameter of between 0.5 millimeters and 2.0 millimeters.
8. The medical lead of claim 1, wherein the cable conductor is an
insulated cable conductor.
9. The medical lead of claim 1, further comprising an insulating
layer partially covering the helical electrode.
10. The medical lead of claim 1, further comprising a proximal
connector including connector terminals electrically coupled to the
helical electrode, the ring electrode, and the cable electrode.
11. The medical lead of claim 1, wherein the cable conductor has a
cable conductor diameter of 0.51-1.27 millimeters (0.02 to 0.05
inches).
12. The medical lead of claim 11, wherein the lead body has a lead
body diameter of 1-2 millimeters (0.039-0.079 inches).
13. The medical lead of claim 1, wherein the connector includes a
connector pin, wherein the connector pin is configured to
electrically couple to the cable electrode via the cable
conductor.
14. The medical lead of claim 1, wherein the ring electrode is
attached to the lead body.
15. A method for implanting a medical lead, the medical lead
including: a lead body; a connector proximate to a proximal end of
the lead body; a helix extending from a distal end of the lead
body, wherein the helix is configured to anchor to a patient
tissue, and wherein the helix forms a helical electrode; a ring
electrode proximate to the distal end of the lead body; and a cable
within the lead body, the cable including a cable conductor, a
cable electrode proximate a distal end of the cable conductor, and
a blunt dissection tip at a distal end of the cable, wherein the
cable conductor is a solid wire or a stranded wire, and wherein the
cable is slidable within the lead body to drive extension and
retraction of the cable electrode along a trajectory extending from
the distal end of the lead body, the method comprising: securing
the helix of to the patient tissue proximate a target site; and
extending the cable conductor from the lead body to deploy the
cable electrode within the patient tissue past a distal end of the
helix.
16. The method of claim 15, wherein extending the cable conductor
from the lead body extends the cable electrode at least 1.8
centimeters from the distal end of the lead body.
17. The method of claim 15, wherein securing the helix of the
medical lead to the patient tissue includes: positioning a distal
end of a catheter proximate the target site; delivering a distal
end of the medical lead proximate the target site via the catheter;
and rotating the helix to anchor the helix to the patient
tissue.
18. The method of claim 17, further comprising, after securing the
helix, manipulating the catheter to set the trajectory for
deploying the cable electrode within the patient tissue, wherein
manipulating the catheter includes one or more of: bending the
catheter through pushing and pulling from a proximal location
outside the body of the patient; and rotating the catheter.
19. The method of claim 15, wherein deploying the cable electrode
within the patient tissue includes blunt dissection of the patient
tissue with the cable electrode.
20. The method of claim 15, wherein the target site is a septum of
the patient.
21. The method of claim 15, wherein deploying the cable electrode
within the patient tissue comprises deploying the cable electrode
within the patient tissue to contact a left bundle branch of the
patient.
22. The method of claim 15, wherein the target site is a septum of
the patient, wherein, with the helix is anchored to the patient
tissue and the cable electrode deployed within the patient tissue,
the cable electrode is proximal to a left bundle branch and a right
bundle branch of the patient, and wherein, with the helix is
anchored to the patient tissue and the cable electrode deployed
within the patient tissue, the helical electrode is proximal to the
right bundle branch.
23. The method of claim 15, wherein the cable conductor has a cable
conductor diameter of 0.51-1.27 millimeters (0.02 to 0.05
inches).
24. The method of claim 23, wherein the lead body has a lead body
diameter of 1-2 millimeters (0.039-0.079 inches).
25. The method of claim 15, wherein the ring electrode is attached
to the lead body.
26. A medical lead comprising: a lead body; a connector proximate
to a proximal end of the lead body; a helix extending from a distal
end of the lead body, wherein the helix is configured to anchor to
a patient tissue; a ring electrode proximate to the distal end of
the lead body; and a cable within the lead body, the cable
including a cable conductor, a first cable electrode proximate a
distal end of the cable conductor, a second cable electrode
proximal the first cable electrode and a blunt dissection tip at a
distal end of the cable, wherein the cable conductor includes two
solid or stranded wires, one coupled to the first cable electrode
and another coupled the second cable electrode, wherein the cable
is slidable within the lead body to drive extension and retraction
of the first cable electrode and the second cable electrode along a
trajectory extending from the distal end of the lead body, and
wherein, when the helix is anchored to the patient tissue, the
blunt dissection tip is configured to blunt dissect the patient
tissue along the trajectory extending from the distal end of the
lead body and past a distal end of the helix through extension of
the cable.
27. The medical lead of claim 26, wherein the cable conductor has a
cable conductor diameter of 0.51-1.27 millimeters (0.02 to 0.05
inches).
28. The medical lead of claim 27, wherein the lead body has a lead
body diameter of 1-2 millimeters (0.039-0.079 inches).
29. The medical lead of claim 26, wherein the connector includes a
connector pin, wherein the connector pin is configured to
electrically couple to the first cable electrode via the cable
conductor.
30. The medical lead of claim 26, wherein the ring electrode is
attached to the lead body.
31. A method for implanting a medical lead, the medical lead
including: a lead body; a connector proximate to a proximal end of
the lead body, wherein the connector includes a connector pin; a
helix extending from a distal end of the lead body, wherein the
helix is configured to anchor to a patient tissue, and wherein the
helix forms a helical electrode; a ring electrode proximate to the
distal end of the lead body; and a cable within the lead body, the
cable including a cable conductor, a cable electrode proximate a
distal end of the cable conductor, and a blunt dissection tip at a
distal end of the cable, wherein the cable conductor is a solid
wire or a stranded wire, and wherein the cable is slidable within
the lead body to extend and retract the cable electrode along a
trajectory extending from the distal end of the lead body, the
method comprising: securing the helix of to the patient tissue
proximate a target site; extending the cable conductor from the
lead body to deploy the cable electrode within the patient tissue;
after deploying the cable electrode within the patient tissue,
cutting the cable; and electrically coupling the connector pin to
the cable electrode via the cable conductor.
Description
TECHNICAL FIELD
This disclosure relates to cardiac pacing.
BACKGROUND
Typically, pacing leads are deployed to various locations in the
heart depending on the nature of the heart condition necessitating
the pacing procedure. Conventional ventricular pacing typically
involves implanting a lead at the apex of the right ventricle. This
placement is still often utilized today even in the face of
published evidence of the deleterious effects of bypassing the
His/Purkinje system, otherwise known as the cardiac conduction
system.
Pacemaker lead electrodes have been regularly placed in or on the
heart in a position that bypasses the His/Purkinje system since the
inception of pacing in 1957. Conventional pacing directly
stimulates the myocardium and has been the standard of care even
though His bundle pacing has been known and tried occasionally.
During and around the 1980s, scientific studies found that over
time, ventricular pacing resulted in what was termed, "ventricular
remodeling," which can result in a number of detrimental effects
including: myofiber disarray, fatty tissue and fibrotic deposits
away from the electrode, impaired endothelium function, acute
hemodynamic compromise, redistribution of myocardial fiber strain
and blood flow, with hypertrophy away from the electrode, mitral
valve regurgitation due to poor papillary muscle timing, cardiac
sympathetic activity, decreases in left ventricle (LV) chamber
efficiency, slowing of LV isovolumic relaxation, far LV wall
contracting against a closed aortic valve, tricuspid valve
insufficiency due to lead mechanical disruption, and mitochondrial
abnormality away from the electrode.
By 2002, large, controlled studies found that conventional
ventricular pacing also resulted in heart failure hospitalization
and mortality, especially when the patient was paced forty percent
or more or the time. This iatrogenic problem is referred to as
"pacing induced heart failure."
In spite of significant research demonstrating significant
mortality reductions for His bundle pacing compared to conventional
pacing, the value of His pacing has not been widely recognized or
practiced among clinicians responsible for implanting cardiac
pacing leads and pacemakers.
BRIEF SUMMARY
The inventors believe the limited prevalence of His bundle pacing,
and when required, pacing the left bundle branch (LBB) of the
conduction system, is in part due to lack of effective leads and
lead delivery systems. The His bundle consists of two discreet
bundles which separate at the crest of the ventricular septum to
form the LBB and right bundle branch (RBB). The cardiac conduction
system is comprised in part of His bundle which resides between the
atrioventricular (AV) node, and the bifurcation of the LBB and RBB.
These anatomic locations are regarded as difficult targets to
reach.
For example, many patients cannot have LBB block corrected by His
bundle pacing but can benefit from LBB pacing. Techniques disclosed
herein facilitate both His bundle pacing, generally via the septal
wall of the right atrium, and LBB pacing, generally via right
ventricle (RV) septal access. The present disclosure describes
examples of leads and methods for use including delivering a pacing
lead to the LBB, at the septal wall of the RV or the His bundle in
the right atrium.
Examples of the present disclosure includes a lead with a distal
helix to facilitate anchoring to the septal wall of the RV
proximate the RBB or, alternatively, proximate the His bundle,
generally via the septal wall of the right atrium. Such leads may
further include a blunt dissection electrode configured for
deployment within the septum. The blunt dissection electrode may be
advanced to the His bundle or LBB following anchoring the distal
end of the lead into the septal wall with the helix. The lead
further includes a second deployed electrode, such as helical
electrode included in the distal helix. The second electrode may be
used to capture the RBB while the first electrode captures the LBB.
In this manner, examples of the disclosed lead facilitate targeting
both the RBB and the LBB with a single lead, e.g., with bifocal
stimulation or for cardiac resynchronization.
The lead may be implanted via a catheter. Implantation techniques
may include selecting a trajectory for the blunt dissention
electrode by manipulating the catheter after anchoring the helix to
the septal wall. For example, with the distal end of the
catheter-lead assembly anchored to the septal wall, the direction
of the trajectory of the blunt dissection electrode may be selected
by the clinician by bending the catheter through pushing and
pulling from a proximal location outside the body of the patient,
as well by rotating the catheter from the outside the body of the
patient.
In one example, this disclosure is directed to a medical lead
including a lead body, a connector proximate to a proximal end of
the lead body, a helix extending from a distal end of the lead
body. The helix is configured to anchor to a patient tissue, and
the helix forms a helical electrode. The medical lead further
includes a ring electrode proximate to the distal end of the lead
body, and a cable within the lead body, the cable including a cable
conductor, a cable electrode proximate a distal end of the cable
conductor, and a blunt dissection tip at a distal end of the cable.
The cable is slidable within the lead body to extend and retract
the cable electrode along a trajectory extending from the distal
end of the lead body. When the helix is anchored to the patient
tissue, the blunt dissection tip is configured to blunt dissect the
patient tissue along the trajectory extending from the distal end
of the lead body through extension of the cable.
In another example, this disclosure is directed to a method for
implanting a medical lead the medical lead including, a lead body,
a connector proximate to a proximal end of the lead body, a helix
extending from a distal end of the lead body, wherein the helix is
configured to anchor to a patient tissue, and wherein the helix
forms a helical electrode, a ring electrode proximate to the distal
end of the lead body, a cable within the lead body, the cable
including a cable conductor, a cable electrode proximate a distal
end of the cable conductor, and a blunt dissection tip at a distal
end of the cable. The cable is slidable within the lead body to
extend and retract the cable electrode along a trajectory extending
from the distal end of the lead body. The method includes securing
the helix of to a patient tissue proximate a target site and
extending the cable conductor from the lead body to deploy the
cable electrode within the patient tissue.
In a further example, this disclosure is directed to a medical lead
including a lead body, a connector proximate to a proximal end of
the lead body, a helix extending from a distal end of the lead
body, wherein the helix is configured to anchor to a patient
tissue, a ring electrode proximate to the distal end of the lead
body, and a cable within the lead body, the cable including a cable
conductor, a first cable electrode proximate a distal end of the
cable conductor, a second cable electrode proximal the first cable
electrode and a blunt dissection tip at a distal end of the cable.
The cable is slidable within the lead body to extend and retract
the first cable electrode and the second cable electrode along a
trajectory extending from the distal end of the lead body. When the
helix is anchored to the patient tissue, the blunt dissection tip
is configured to blunt dissect the patient tissue along the
trajectory extending from the distal end of the lead body through
extension of the cable.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional illustration of a human heart depicting
the anatomy of the heart and its electrical system.
FIG. 2 is a cross-sectional illustration of a human heart wherein
an example of a guide catheter is shown advanced to a target site
within the RV corresponding to the RBB.
FIG. 3 is an anatomical illustration of a patient and the manner in
which the example shown in FIG. 2 initially accesses the
vasculature prior to advancement into the heart.
FIG. 4 is a conceptual illustration of a pacing lead accessing the
septum from the RV in accordance with one example of this
disclosure.
FIGS. 5A-5C illustrate detailed views of the distal region and tip
of the pacing lead while mapping the LBB while attached to and
fixed in a patient's septum.
FIG. 6 illustrates the pacing lead with the proximal blunt
dissection conductor and a self-stripping connector pin.
FIGS. 7A-7C illustrate an alternative lead design with an exposed
helical electrode that facilitates mapping.
FIG. 8 is a flowchart illustrating techniques for locating a lead
electrode proximate the LBB and RBB for cardiac resynchronization
therapy.
FIG. 9 illustrates an alternative lead design with a helix
partially covered by an insulating layer.
FIG. 10 illustrates an alternative lead design with an insulated
helix fully covered by an insulating layer and a cathode ring on
the distal end of the lead body.
FIG. 11 illustrates an alternative lead design including two cable
electrodes.
DETAILED DESCRIPTION
The prevalence of His bundle pacing or LBB pacing, though
increasing, is practiced in a small minority of pacing lead
implantations both in the United States and worldwide. The His
bundle and LBB present a small targets and are hard to reach
successfully. This increases fluoroscopy or "flouro" time, which is
a detriment to both patient and the surgical clinician. However, in
one study by the inventors, the mortality rate of one hospital
doing conventional pacing was compared with the mortality rate with
another hospital doing pacing at the His bundle (for normal
physiological ventricular activation). Heart failure and patient
mortality was lower at the hospital providing physiological
ventricular activation by His bundle pacing.
It is generally more difficult to place a cardiac lead electrode at
the conduction system for His bundle pacing or LBB pacing than it
is to place within the RV for conventional pacing. However,
techniques of the present disclosure mitigate difficulties with
locating a lead electrode to capture the His bundle or LBB.
Locating a lead electrode to capture the LBB, which is important
for patients with LBB block in which the capturing the His bundle
may not provide effective LBB normalization. Disclosed techniques
also facilitate capturing the RBB, e.g., for bifocal stimulation
and/or to facilitate cardiac resynchronization.
In one example, a lead includes an anode ring electrode, and a
helical electrode anchor configured to be anchored on the septum of
the right atrium, piercing the endocardial membrane of the right
atrium. The helical electrode may capture the RBB. A blunt
dissection electrode is connected via a cable conductor extending
from the connector end of the lead. A clinician advances the cable
conductor through the coaxial center of the lead, advancing the
blunt dissection electrode via the pierced endocardial membrane of
the RV to a targeted portion of the cardiac conduction system,
usually the His bundle within the septum or extending distally to
the LBB.
The trajectory of the blunt dissection electrode is controlled by
the angle of the lead delivery catheter following anchoring of the
helical electrode anchor. While anchored, the clinician may
manipulate the angle of lead delivery catheter. The catheter pivots
the helical electrode, controlling the trajectory of the blunt
dissection electrode.
In this manner, the catheter and fixation screw need not be
presented at any particular angle (such as perpendicular) to the
endocardial surface. The trajectory of the blunt dissection
electrode can be manipulated after helical electrode fixation and
has no bearing on His pacing threshold. Thus, a variety of lead
delivery catheters may be suitable for delivery of leads disclosed
herein.
Once the clinician is satisfied with the angle of the catheter, the
clinician advances the cable, having the blunt dissection electrode
attached at the distal tip, is advanced from the connector end,
through the lead body and helical electrode to the targeted portion
of the cardiac conduction system, e.g., via blunt dissection. In
other examples, the tissue may be cut with a sharp electrode or RF
energy. However, blunt dissection may provide an advantage of
mitigating the risk of piercing the septum as the endocardial
membrane of the ventricular septum provides a relatively durable
and elastic layer resistant to blunt dissection compared to the
muscular central portion of the ventricular septum.
Selection of either specific or nonspecific His bundle pacing can
be achieved for type two His anatomy because of the blunt
dissection electrode is small enough to fit within the His bundle.
Type two His anatomy, existing in an estimated 32% of patients, is
where the His bundle dives below the central fibrous body and is
surrounded by myocardium. Large electrodes, such as helical
electrodes of current leads may be too large to exclude the
myocardium from activation along with the His bundle (called
non-specific His bundle pacing). In contrast, smaller electrodes of
leads disclosed herein, such as those with an electrode radius of
about 0.5 millimeters (mm), allow for "specific" His bundle pacing.
Such smaller electrodes may also facilitate LBB pacing, in the
event that LBB block cannot be corrected at the His bundle due to
infra-hisian block, e.g., through transseptal lead placement.
In contrast, a clinician attempting to use a conventional screw-in
lead meant for RV or atrial endocardial attachment may try to drill
thru the septum--a process that is very tedious, reportedly
requiring at times, forty turns, and having the risk of penetration
into the lumen of the LV risking embolic stroke.
In examples where the helical electrode anchor includes a helical
electrode, which facilitates targeting the RBB, either
simultaneously or independently of the LBB, e.g., for cardiac
resynchronization. The multiple electrode configuration of leads
disclosed herein provide a number of options for stimulation of the
His bundle, RBB and/or LBB. Moreover, stimulation parameters may be
reprogrammed without further surgical intervention if needed to
overcome post-implantation degradation of the hearts conduction
system.
FIG. 1 shows the cardiac anatomy, especially the cardiac conduction
system. In a healthy heart, the natural pacemaker, the SA node,
activates the high conduction velocity Purkinje fibers within the
right and left atria, resulting in coordinated atrial muscle cell
contraction. This injects blood collected in the atria, into the
powerful left and right ventricles. There is a pause in conduction
at the AV node allowing the ventricles to fill. Then, just before
blood flows back into the atria, the AV node activates the His
bundle and, by high conduction velocity, the left and right bundle
branches and the entire Purkinje system. This choreographs
ventricular contraction, endocardial myocardium contracting first
followed by epicardial muscle contraction. This programmed
ventricular muscle activation produces an efficient pumping action
that not only squeezes blood out of the ventricles but produces
kinetic energy as blood is accelerated from the ventricles. The
result of conventional pacing is compromised Hemodynamics due to
slow cell-to-cell conduction and an aberrant ventricular activation
sequence as the cardiac conduction system is bypassed. The far-left
ventricular wall away from the electrode site has been seen
contracting against an already closed aortic valve.
For contextual understanding of how examples of the disclosure are
intended to function, FIG. 1 is included to illustrate the
structure of a typical human heart 1 with relevant anatomical
features shown. As mentioned, one example of the disclosure is
directed to a method for deploying an electrical lead to the LBB 5,
potentially accessed from target site 10 on ventricular septum 3
from within the RV 12. Such a target site 10 for proper deployment
of a pacing lead, is depicted in FIG. 1 against the wall of
ventricular septum 3 below tricuspid valve septal leaflet 7 within
RV 12. Targeting LBB 5 is particularly useful for patients
experience LBB block. Examples may simultaneously target the LBB
and RBB to facilitate dual bipolar, dual unipolar pacing, and/or
cardiac resynchronization therapy. Nonspecific bundle branch pacing
(conduction system and nearby myocardium) or contractile myocardium
only pacing of either cathode may be appropriate in some cases.
In other examples, the target site may be the His bundle 2 at the
septum 3 distal to the atrioventricular (AV) node 4, but proximal
to the LBB 5 and the RBB 6. Such a target site for proper
deployment of a pacing lead into the His bundle is at the crest of
the ventricular septum 3 on the atrial aspect of the annulus of the
tricuspid valve septal leaflet 7 within the right atrium 8.
FIG. 2 is the schematic diagram of FIG. 1 in which a distal portion
or end region 22 of delivery catheter 20 is shown extending into
the RV 12 of the heart 1, from the superior vena cava 9 and the
left subclavian vein 11, with the distal tip 24 positioned at the
target site 10.
Typically, left pectoral side approach is desired. It involves
accessing the heart via the left subclavian vein, the cephalic vein
and more rarely the internal or external jugular vein, or femoral
vein. However, it is also possible to utilize the less common right
pectoral side approach. In either case, for catheter lead
placement, a guide wire 50 may be advanced into the heart 1 from
the access site. Delivery catheter 20 may be advanced through the
vasculature and into the heart 1 over the guidewire; once in
position the guidewire is removed. A pacing lead is then advanced
through the guiding catheter 1 to be deployed at various regions in
the heart.
According to one method, a clinician positions guide wire 50 into
the heart 1, for example via a "sub-clavian stick" or central
venous access procedure such as is illustrated in FIG. 3.
Accordingly, the catheter 20 is passed over the guide wire and
advanced into the superior vena cava 9 from the left subclavian
vein 11 through right atrium 8 and tricuspid valve septal leaflet 7
and into the RV 12 such as is in the manner shown in FIG. 2.
FIG. 4 illustrates a tripolar, or more specifically, a dual
bipolar, medical electrical lead 30 in accordance with one example
of this disclosure. Medical electrical lead 30 includes a helical
electrode 32 and anode ring electrode 37, which are electrically
coupled to connector terminals 41, 42. Medical electrical lead 30
further includes a central cable conductor 33 terminating at blunt
dissection electrode 34 and extending within a central lumen of
lead 30 about a length of lead body 38 for coupling to connector
pin 44 of proximal connector 40.
Cable conductor 33 includes one or more conductive elements forming
an electrical connection between blunt dissection electrode 34 and
connector pin 44 once connector pin 44 is connected to the
conductive elements of cable conductor 33. In various examples,
cable conductor 33 may include a solid wire conductor, a stranded
wire, or a coil conductor. In a particular example, cable conductor
33 may include a fiber core coil with one or more electrically
conductive wires coiled on a fiber core. The fiber core may provide
tensile strength for cable conductor 33 and mitigate stretching of
the coiled conductors during retraction of cable conductor 33.
In the same or different examples, cable conductor 33 may be an
insulated cable conductor including outer insulating layer, leaving
the distal tip exposed for blunt dissection electrode 34. The
insulating layer may include silicone rubber, polyurethane
parylene, polymide and/or ethylene tetrafluoroethylene (ETFE) cable
insulation. In some examples, connector pin 44 may be a
self-stripping connector pin 44 to allow contact with the
conductive elements of cable conductor 33. Alternatively, connector
pin 44 may make electrical contact with conductive elements of
cable conductor 33 upon tightening of a setscrew of the connector
of a pulse generator or other device connected to proximal
connector 40. Central cable conductor 33 is slidable the central
lumen of lead body 38 to extend and retract blunt dissection
electrode 34 relative to the distal end of lead body 38.
In the same or different examples, blunt dissection electrode 34
may be a unitary component with the conductive element(s) of cable
conductor 33 or may be a separate component physically and
electrically coupled to the distal end of the conductive element(s)
of cable conductor 33, for example, by solder or welding, such as
laser welding. Blunt dissection electrode 34 forms a rounded
frontal surface extending across a width of the cable. In some
examples, the blunt dissection electrode 34 is a 0.5 to 2.0 mm
diameter, such as 0.7 to 1.0 mm diameter hemispherical electrode,
such as a half sphere with a diameter of about 0.87 mm, at the end
of an insulated blunt dissection electrode conductor of the same
diameter in order to provide blunt dissection. In the same or
different examples, the electrode proximate the distal end of cable
conductor 33 may be a ring electrode instead of a tip electrode
(such as electrode 535 of lead 530 in FIG. 11).
Medical electrical lead 30 includes a second conductor within lead
body 38 extending between ring terminal 41 and anode ring electrode
37. Medical electrical lead 30 further includes a third conductor
within lead body 38 extending between ring terminal 42 and helical
electrode 32. In some examples, the second conductor and the third
conductors are coaxial, insulated coil conductors surrounding the
central cable conductor 33 within the lead body 38. The insulation
should be selected to provide low friction with the central cable
conductor 33. For example, the insulation of the coil conductors
may be a low friction important polymer material, such as silicone
rubber, polyurethane, parylene, polymide and/or ETFE or other
non-conductive material. Likewise, central cable conductor 33 may
be insulated with a low-friction material or include a low-friction
coating, such as silicone rubber, polyurethane, parylene, polymide
and/or ETFE.
Helical electrode 32 may be made from a wire, such as a platinum
alloy or other biocompatible metal. The number of turns and length
of the helix may be adapted for a particular application. For
example, helical electrode 32 may have 1 to 8 turns, such as 2 to 4
turns to support adequate fixation within patient tissue. A septal
thickness can be anywhere from 0.9 to 1.2 centimeters in normal
individuals. A risk of perforation will likely go up if the helix
is too long and the entire helix penetrates the septum.
Accordingly, the dimensions of the helix should be selected to
allow fixation and capture of the RBB but mitigate a risk of
perforation. In the present example, a helix length of 1.0 to 8.0
mm may be appropriate to mitigate a risk of piecing the septum,
such as a helix length of 1.5 to 4 mm, such as about 1.8 mm. As
used herein, the term about means within a range of tolerances of
manufacturing techniques used to produce the referenced
element.
Anode ring electrode 37 is coplanar with an outer surface of lead
body 38. The spacing and surface area of anode ring electrode 37 is
selected to provide support stimulation via both helical electrode
32 and blunt dissection electrode 34. In some examples, anode ring
electrode 37 may have a spacing of between 5 to 15 mm from helical
electrode 32, such as a spacing of between 7 to 10 mm, such as a
spacing of about 9 mm. In the same or different examples, anode
ring electrode 37 may have a surface area of between 10 to 30
square mm, such as a surface area of between 15 to 20 square mm,
such as a surface area of about 16.9 square mm.
In one particular example of lead 30, the following dimensions may
be used. Lead body 38 diameter 3 to 6 French, such as about 4.1
French, cable conductor 33 diameter, 0.02 to 0.05 inches, such as
about 0.028 inches, helical electrode 32 length 1 to 4 mm, such as
about 1.8 mm, helical electrode 32 pitch, 0.5 to 2 mm, such as
about 1 mm, helical electrode 32 wire diameter 0.1 to 1.0 mm, such
as about 0.3 mm. In the same or different examples, a platinum
alloy may be utilized for the helical electrode 32 wire such as Pt
80%/Ir 20% or Pt 90%/Ir 10% for a thinner wire.
As used herein, the terms anode and cathode merely represent
example uses of particular lead electrodes. For example, anode ring
electrode 37, helical electrode 32, and blunt dissection electrode
34 are electrically isolated within medical lead 30 such that such
that any two of anode ring electrode 37, helical electrode 32, and
blunt dissection electrode 34 may form an electrode pair to deliver
stimulation. However, the polarity of the stimulation is controlled
by a pulse generator and not inherent to the structure of
electrical lead 30 itself. Thus, the pulse generator could reverse
the polarity of anode ring electrode 37, helical electrode 32, and
blunt dissection electrode 34, use any two electrodes as an
anode-cathode pair, or even use one or more of anode ring electrode
37, helical electrode 32, and blunt dissection electrode 34 in a
unipolar configuration in combination with the pulse generator
housing.
In FIG. 4, a close-up view of the distal tip 24 of the catheter 20
is shown following advancement of medical electrical lead 30 though
a lumen of the catheter 20 to the target site 10. In this example,
the target site for blunt dissection electrode 34 is the LBB,
although the His bundle can also be targeted.
The lead 30 is extended distally from catheter distal tip 24,
exposing helical electrode 32. At this point, the clinician may map
of the RBB with the helical electrode 32 evaluate capture
threshold. If desired, the clinician may adjust the position of the
distal tip 24 of the catheter 20 adjacent the septal wall to
improve capture of the RBB before proceeding to anchor the helical
electrode 32.
The lead 30 is anchored into the septum 3 by clockwise rotation of
the lead body 38 targeting the RBB, so that helical electrode 32
screws through the endocardial membrane and into the septal wall.
The clinician may again map of the RBB with the helical electrode
32 to confirm capture threshold. If desired, the clinician may
adjust the position of helical electrode 32 within the septal wall
to improve capture of the RBB before proceeding to extend blunt
dissection electrode 34.
The blunt dissection electrode 34 is extended into the septum 3 to
provide pacing to the heart 1 via the LBB. The blunt dissection
electrode 34 punctures the endocardial membrane in the center of
helical electrode 32. In some examples, cable conductor 33 and
blunt dissection electrode 34 may enlarge the perforation in the
endocardial membrane created by helical electrode 32. In other
examples, cable conductor 33 may be withdrawn from lead body 38 and
a needle or stylet (not shown) may be used to puncture the
endocardial membrane. In further examples, RF energy may be applied
to cable conductor 33 to cross the RV endocardium, then detaching
the RF connection to cable conductor 33 and advance it to the LV
endocardium. No matter the technique used to puncture the
endocardial membrane, blunt dissection electrode 34 pushes through
septal tissue using blunt dissection. With the blunt dissection
electrode 34 targeting the LBB, the helical electrode 32 is
proximate the RBB, facilitating cardiac resynchronization therapy
by independently activating helical electrode 32 and blunt
dissection electrode 34.
The use of a stylet or needle may be particularly advantages for
puncturing tissues with more toughness than the septal wall within
the right atrium. For example, if targeting the His bundle from the
right ventricle, a stylet or needle may be used to penetrate the
central fibrous body. In one contemplated example, a clinician may
first target the His bundle from the septal wall within the right
atrium.
While blunt dissection electrode 34 is the preferred configuration
of cable conductor 33 for use in septal implantation, other
configurations of cable conductor 33 are also possible, including a
pointed tip instead of blunt dissection electrode 34.
FIGS. 5A-5C illustrate detailed views of the distal region and tip
of the pacing lead at a target site in a patient's septum.
Specifically, FIG. 5A shows the trajectory of the blunt dissection
electrode direction for mapping of the LBB during catheter
introduction of the lead 30, while FIG. 5B shows a closeup of the
lead delivery catheter and lead tip. The helical electrode 32 for
lead attachment is shown anchored and is pivoted by the lead
delivery catheter.
FIG. 5C shows the LBB mapping process and possible range of blunt
dissection electrode location. Mapping for lead location is
accomplished by sensing the LBB potential and/or pacing the LBB to
produce a narrow QRS on the surface ECG, typical of physiologically
normal ventricular activation. The trajectory of the blunt
dissection electrode advancement is controlled by manipulation of
the lead delivery catheter. Resistance to advancement of cable
conductor 33 is felt when the electrode 34 impinges on the tough
left ventricular endocardial membrane. See the tenting effect of
the opposite endocardial membrane in FIG. 5C.
FIG. 6 illustrates lead 30 including a proximal connector 40 with a
self-stripping connector pin 44. After selecting a proper lead
position in the heart, cable conductor 33 is cut flush with the
connector pin 44. The pulse generator's connector setscrew is
tightened to make electrical contact, fracturing the cable
insulation, and completing the circuit to blunt dissection
electrode 34. The setscrew also fixes the relative position of
cable conductor 33 to proximal connector 40. Also illustrated is
proximal ring terminals 41, 42, 43 located adjacent and distal to
connector pin 44. Ring terminal 41 provides an electrical
connection to anode ring electrode 37, while ring terminal 42
provides an electrical connection to cathode electrode 32. Ring
terminal 43 may provide a redundant connection to one of electrodes
34, 32, 37 or a connection to an optional fourth electrode (not
shown), such as a second distal electrode on lead body 38, either
proximal or distal to electrode 37.
In other examples, a proximal end of cable conductor 33 may include
an exposed conductor the same diameter as the pin electrode of an
IS-4 connector, or other industry standard connector. In such
examples, the exposed conductor may simply be cut to the proper
length after extending blunt dissection electrode 34 to the target
site. In such examples, collapsible connector pin 44 is not
required as the exposed proximal end of cable conductor 33 itself
serves as the pin electrode of connector 40. The pulse generator's
connector setscrew secures the position of cable conductor 33
relative to the connector body.
The example proximal connector 40 illustrated in FIG. 6 conforms to
the IS-4 standard. In various examples, connector 40 may conform to
a standard pulse generator connector, such as an IS-1, IS-4, DF-1,
DF-4, or other industry standard connector.
FIG. 7A-7C illustrate the distal end of a medical electrical lead
130, which provides an alternative lead design as compared to
medical electrical lead 30. With this example, a helical electrode
132 is attached over the lead delivery catheter tip 124. This
exposes the helical electrode 132 for mapping purposes. As shown in
FIG. 7A, helical electrode 132 extends through slot 122 which
extends along a length of delivery catheter 120 at lead delivery
catheter tip 124. The pointed distal tip of helical electrode 132
is closely fitted to the catheter outer diameter to prevent
snagging on inter-vascular tissue during venous passage of the
catheter lead assembly. Deployment of helical electrode 132, e.g.,
through extension of cable conductor 133 in direction 141, then
turning lead 130 relative to the patient tissue in direction 142
(corresponding to the curvature of helical electrode 132) anchors
the distal tip of helical electrode 132 in the patient tissue.
Similar to lead 30, lead 130 includes an anode ring electrode 137.
Lead 130 also includes a blunt dissection electrode 134, the
trajectory of which is selectable by a clinician by manipulating
the catheter lead assembly after anchoring helical electrode 132
within a tissue of the patient, such as the septal wall. This
design of catheter 120 and lead 130 may increase the percutaneous
introduction size, such as by 2 French as compared to catheter 20
and lead 30. Following the selection of the trajectory, the
clinician may deploy electrode 134 within the patient tissue along
direction 143, representing the selected trajectory, through
extension of cable conductor 133 by pushing cable conductor 133
relative to helical electrode 132 of lead 130.
FIG. 8 is a flowchart illustrating techniques for locating a lead
electrode to pace the cardiac conduction system, to allow capture
of both the RBB and LBB. For clarity, the techniques of FIG. 8 are
described with respect to catheter 20 and medical electrical lead
30, although the techniques may likewise be applied to medical
electrical leads 130, 330, 430, 530 and to variations of the
example leads disclosed herein.
First, a clinician positions the distal tip 24 of catheter 20 at
the target site 10 on a patient's septum within the RV (FIG. 8,
step 202). In some example, a guidewire may be used to direct the
catheter to target site 10. Once, the distal tip 24 of catheter 20
is positioned at the target site 10, the clinician removes
guidewire (if any) and introduces lead 30 via the central lumen of
the catheter 20. The distal end of lead 30 is delivered to the
target site 10 in the septum via catheter 20 (FIG. 8, step 204). In
other examples, lead 30 may be introduced with a stylet, after
temporarily extracting the central cable conductor 33 from the
central lumen of lead 30. The relatively stiff stylet may also be
used by, blunt dissection, to clear a pathway through tough tissue
such as the central fibrous body for His bundle pacing or along the
left ventricular septum paralleling the LBB, especially when a
relatively flexible cable conductor 33 is desirable.
For mapping, the clinician exposes the helical electrode 32 out the
distal tip 24 of catheter 20 (FIG. 8, step 206). The clinician may
test pacing capture threshold with helical electrode 32. For
example, the clinician may test capture threshold of the RBB to
find a suitable target site for the implantation. The clinician
adjusts the location of the distal tip 24 of catheter 20 to select
a target site for the implantation while testing pacing capture
threshold with helical electrode 32 (FIG. 8, step 210).
The clinician anchors the catheter lead assembly to the target site
10 in the septum by rotating the lead 30 to engage the septum with
the helical electrode 32 of lead 30 (FIG. 8, step 212). Preferably,
to limit flouro time and trauma to patient tissue, helical
electrode 32 is only anchored a single time, but the clinician may
withdraw and anchor the helical electrode 32 if the pacing or
sensing capture threshold is undesirable.
After securing the helix, the clinician may then manipulate the
catheter 20 to set a desired trajectory for blunt dissection of the
septum with the blunt dissection electrode blunt dissection
electrode 34 (FIG. 8, step 214). For example, the clinician may
select a trajectory for the blunt dissention electrode by
manipulating the catheter after anchoring the helical electrode to
the septal wall by bending the catheter through pushing and pulling
from a proximal location outside the body of the patient, as well
by rotating the catheter from the outside the body of the patient.
Once helical electrode 32 is fixed to the septum, the septal wall
is punctured and the blunt dissection electrode can be advanced, by
blunt dissection between about 0.9 to 1.8 centimeters in an adult
patient from the base of helical electrode 32, toward the LBB, just
inside left ventricular septum (FIG. 8, step 216).
For mapping, the clinician may optionally withdraw the blunt
dissection electrode 34 (FIG. 8, step 220), set a new desired
trajectory, and redeploy the blunt dissection electrode 34.
Generally, however, a clinician will only want to retract and
redeploy the blunt dissection electrode 34 if sensing or pacing
capture threshold is undesirable (FIG. 8, step 218). If mapping
finds adjustment is necessary, blunt dissection electrode 34 is
extracted to helical electrode 32 and helical electrode 32 can be
pivoted to a desired new trajectory for advancement of cable
conductor 33.
Examples may simultaneously target the LBB and RBB to facilitate
dual bifocal, dual bipolar or unipolar pacing, for cardiac
resynchronization therapy. Nonspecific bundle branch pacing
(conduction system and nearby myocardium) or contractile myocardium
only specific bundle branch pacing of either cathode may be
appropriate in some cases.
Cathodal voltage stimulation of the LBB via blunt dissection
electrode 34 and cathodal voltage stimulation of the RBB via
helical electrode 32 can be independently adjusted to suit the LBB
pacing voltage threshold and the RBB pacing voltage threshold
independently to produce LV/RV synchrony. Alternatively, lead 30
may be operated to provide dual bifocal stimulation. In one
example, the dual bifocal stimulation may operate ring electrode 37
as the anode and alternatively using blunt dissection electrode 34
and helical electrode 32 as cathodes. In another example, the dual
bifocal stimulation may operate helical electrode 32 as the anode
with and blunt dissection electrode 34 as the cathode alternated
with operating ring electrode 37 as the anode with and helical
electrode 32 as the cathode.
With His bundle, RBB and LBB pacing, pacing threshold voltage is
generally greater than that of conventional pacing, but current
threshold is generally less than that of the electrode of
conventional pacing leads having higher electrode surface area,
thus lower pacing impedance, so that the battery drain is
comparable or better than with to conventional pacing. Blunt
dissection electrode pacing impedance may be on the order of 1,000
ohms.
Blunt dissection electrode 34 forms a rounded frontal surface
extending across a width of the cable. In some examples, the blunt
dissection electrode 34 is a 0.7 to 1 mm diameter hemispherical
electrode at the end of an insulated conductor of the same diameter
in order to provide blunt dissection. This relatively small surface
area (of about one square mm) for the exposed electrode may provide
one or more advantages. For example, the smaller area may
facilitate a reduced battery drain. Micro-dislodgement issues with
other small pacing electrodes should be limited due to the embedded
myocardial electrode placement of blunt dissection electrode 34 as
opposed to placement on the endocardial surface as is the case for
conventional tined leads. Thus, the disclosed techniques may
mitigate instances of micro-dislodgement as can occur with
electrodes positioned on the surface of a patient tissue.
In the same or different examples, the hemispherical tip electrode
34 of cable conductor 33 may be coated with a steroid to mitigate
scar tissue and its negative effects on capture threshold over
time.
While lead 30 may optionally be used to target the His bundle from
the right atrium, occasionally, His bundle pacing (at the crest of
the ventricular septum and within the right atrium) cannot correct
LBB block. LBB block cannot be corrected by His bundle pacing in as
many as 30-40% of patients due to infra-hisian block. When that
happens, cable conductor 33 may be retracted and the trajectory of
cable conductor 33 adjusted to target the LBB. Specifically, the
clinician may target the LBB from with the right atrium without
repositioning the anode helix, rather than from the RV as described
previously. In such examples, the previously anchored anode helix
can be pivoted about ninety degrees to align with the ventricular
septum. When cable conductor 33 is advanced, blunt dissection
electrode 34 slides along the endocardial membrane of the left
ventricle, targeting the LBB, thereby bypassing the infra-hisian
block.
When used for His pacing, particularly when the LBB block cannot be
corrected at the His bundle due to distal block, blunt dissection
electrode 34 is retracted. The catheter is rotated to a blunt
dissection electrode trajectory that aims at the LBB. The blunt
dissection electrode is then advanced along the left ventricular
endocardial membrane to pace the LBB. In such examples, lead 30 may
be used to apply bifocal stimulation to the LBB with electrode 34
and either of two electrodes 32, 37 or trifocal stimulation using
all three electrodes 34, 32, 37. The blunt dissection tip mitigates
the risk of puncturing the septal wall of the left ventricle. Such
examples allow a clinician to first target the His bundle from the
right atrium and adjust to the LBB if needed within limited flouro
time.
Once the position of the blunt dissection electrode 34 is
satisfactory, the clinician may withdraw catheter 20, cut the cable
conductor 33 flush with connector pin 44, insert proximal connector
40 into the pulse generator's connector, and tighten the setscrew
to cut through the insulation and complete the circuit (FIG. 8,
step 222). In examples in which the pulse generator is an
implantable pacemaker, the clinician then inserts the implantable
pacemaker in a pocket under the skin in the patient's chest and is
ready for sensing and/or pacing via the lead 30.
FIG. 9 illustrates medical electrical lead 330. Lead 330 is
substantially similar to lead 30 except that lead 330 includes an
insulating layer 331 over the distal portion of helical electrode
332, partially covering helical electrode 332. The insulating layer
331 limits the exposed anode 335 surface area, increasing field
density adjacent anode helical electrode 332 to allow for bifocal
stimulation. In all other aspects, lead 330 is the same as lead 30.
For brevity, details discussed with respect to lead 30 are
discussed in limited or no detail with respect to lead 330.
Medical electrical lead 330 includes an anode ring electrode 337.
Lead 330 also includes a central cable conductor 333 with blunt
dissection electrode 334, and conductor for electrodes 332, 337. In
some examples, the conductors for electrodes 332, 337 are coil
conductor surrounding central cable conductor 333 within the lead
body 338. In the same or different examples, the central cable
conductor 333 may include an insulated conductor, such as a solid
wire, a stranded wire, or a coil conductor.
Blunt dissection electrode 334 forms a rounded frontal surface
extending across a width of the cable. In some examples, the blunt
dissection electrode 334 is a 0.5 to 2 mm diameter, such as 0.7 to
1 mm diameter hemispherical electrode, such as a half sphere with a
diameter of about 0.87 mm, at the end of an insulated blunt
dissection electrode conductor of the same diameter in order to
provide blunt dissection. In the same or different examples, the
following materials may be utilized for the helical electrode 332
wire: Pt 80%/Ir 20% or Pt 90%/Ir 10% for a thinner wire. In the
same or different examples, the insulating layer 331 over anode
helical electrode 332 may be any suitable dielectric material, such
as a polymer material, such as silicone rubber, polyurethane,
parylene, polymide and/or ETFE or other non-conductive
material.
The configuration of lead 330 provides reduced helical pacing
current threshold compared to lead 30. Such a configuration may be
particularly useful when right septal bifocal stimulation is
desired for example. Such pacing may be useful to support LV/RV
synchronization.
A ratio of anode to blunt dissection electrode surface area should
be selected to support bipolar pacing. In some examples, the anode
to blunt dissection electrode area ratio should be in 2:1 to 30:1,
such as 4:1 to 20:1, such as about 16:1. In one particular example
of lead 330 the following dimensions may be used. Lead 330 diameter
5 French, cable conductor 333 diameter 0.9 mm, helical electrode
332 length 1.8 mm, helical electrode 332 pitch 1 mm, helical
electrode 332 wire diameter 0.3 mm, blunt dissection electrode 334
surface area 1.2 mm.sup.2, exposed anode 335 surface area 20
mm.sup.2.
FIG. 10 illustrates medical electrical lead 430. Medical electrical
lead 430 includes an insulating layer 431 fully covering portion of
helix 432. Medical electrical lead 430 further includes a ring
electrode 439 on the distal end of lead body 438. In other
examples, ring electrode 439 may be partial ring electrode. In the
same or different examples, helix 432 is laser welded to ring
electrode 439. In the same or different examples, ring electrode
439 may be on a distal portion of lead body 438, but not
necessarily on the distal tip of lead body 438. Lead 430 is
otherwise substantially similar to lead 30.
In the configuration of medical electrical lead 430, ring electrode
439 may serve as the second cathode and/or an anode to provide
bipolar stimulation in combination with blunt dissection electrode
434. In all other aspects, lead 430 is the same as lead 30. For
brevity, details discussed with respect to lead 30 are discussed in
limited or no detail with respect to lead 430.
Medical electrical lead 430 includes an anode ring electrode 437
proximal to proximal to helix 432. Lead 430 also includes a central
cable conductor 433 for a blunt dissection electrode 434, as well
as a conductors for electrodes 437, 439. In some examples, the
conductors for electrodes 437, 439 are coaxial, insulated coil
conductors surrounding the central cable conductor 433 within the
lead body 438. In the same or different examples, the central cable
conductor 433 may include an insulated conductor, such as a solid
wire, a stranded wire, or a coil conductor.
Blunt dissection electrode 434 forms a rounded frontal surface
extending across a width of the cable. In some examples, the blunt
dissection electrode 434 is a 0.5 to 2 mm diameter, such as 0.7 to
1 mm diameter hemispherical electrode, such as a half sphere with a
diameter of about 0.87 mm, at the end of an insulated blunt
dissection electrode conductor of the same diameter in order to
provide blunt dissection. In the same or different examples, the
following materials may be utilized for the helix 432 wire: Pt
80%/Ir 20% or Pt 90%/Ir 10% for a thinner wire. In the same or
different examples, the helix coating 431 may be any suitable
dielectric material, such as a polymer material, such as parylene,
polymide or other non-conductive material.
Like lead 330, the configuration of lead 430 provides reduced
helical current pacing threshold compared to lead 30. Such a
configuration may be particularly useful when right septal bipolar
stimulation is desired for example. A ratio of anode (such as ring
electrode 439) to blunt dissection electrode surface area should be
selected to support bifocal pacing. In some examples, the anode to
blunt dissection electrode area ratio should be in 2:1 to 30:1,
such as 4:1 to 20:1, such as about 16:1.
Such pacing may be useful to support LV/RV synchronization. For
example, cathodal voltage stimulation of the LBB via blunt
dissection electrode 434 and cathodal voltage stimulation of the
RBB via electrode 439 can be independently adjusted to suit the LBB
pacing voltage threshold and the RBB pacing voltage threshold
independently to produce LV/RV synchrony. Alternatively, lead 430
may be operated to provide dual bifocal stimulation. In one
example, the dual bifocal stimulation may operate ring electrode
437 as the anode and alternatively using blunt dissection electrode
434 and ring electrode 439 as cathodes. In another example, the
dual bifocal stimulation may operate ring electrode 437 as the
anode with and blunt dissection electrode 434 as the cathode
alternated with operating ring electrode 437 as the anode with and
ring electrode 439 as the cathode.
The configuration of lead 430 is also suitable for His bundle
pacing near the endocardial surface by prevention of blunt
dissection electrode shorting to the helical electrode as may occur
with lead 30. Specifically, the location of ring electrode 439
provides further separation between ring electrode 439 and distal
blunt dissection electrode 434 by the endocardial membrane. Such a
configuration may mitigate short circuiting of the electrodes even
with a shallow blunt dissection electrode placement. Such placement
may be particularly useful when the His bundle presents near the
endocardium as a shallow blunt dissection electrode placement would
position the blunt dissection electrode adjacent the His
bundle.
FIG. 11 illustrates medical electrical lead 530. Medical electrical
lead 530 includes a ring electrode 535 on the cable conductor 533.
Medical electrical lead 530 also includes an optional insulating
layer 531 fully covering portion of helix 532. Lead 530 is
otherwise substantially similar to lead 30.
In the configuration of medical electrical lead 530, ring electrode
535 may serve as the second cathode and/or an anode to provide
bifocal stimulation in combination with blunt dissection electrode
534. In all other aspects, lead 530 is the same as lead 30. In
addition, central cable conductor 533 includes two conductors, one
for ring electrode 535, and one for blunt dissection electrode 534.
For brevity, details discussed with respect to lead 30 are
discussed in limited or no detail with respect to lead 530.
Medical electrical lead 530 includes an anode ring electrode 537
proximal to helix 532. Lead 530 also includes a central cable
conductor 533 for a blunt dissection electrode 534 and ring
electrode 539. In such examples, central cable conductor 533
includes at least two insulated conductors and at least two
proximal contacts. In some examples, the central cable conductor
533 including solid wire, stranded wire, or coiled conductor. In
the same or different examples, the anode conductor is a coil
conductor surrounding the central cable conductor 533 within the
lead body 538.
Blunt dissection electrode 534 forms a rounded frontal surface
extending across a width of the cable. In some examples, the blunt
dissection electrode 534 is a 0.5 to 2 mm diameter, such as 0.7 to
1 mm diameter hemispherical electrode, such as a half sphere with a
diameter of about 0.87 mm, at the end of an insulated blunt
dissection electrode conductor of the same diameter in order to
provide blunt dissection. In the same or different examples, the
following materials may be utilized for the helix 532 wire: Pt
80%/Ir 20% or Pt 90%/Ir 10% for a thinner wire. In the same or
different examples, the helix coating 531 may be any suitable
dielectric material, such as a polymer material, such as parylene,
polymide or other non-conductive material.
Like lead 330, the configuration of lead 530 provides reduced
bipolar current pacing threshold compared to lead 30. Such a
configuration may be particularly useful when right septal bifocal
stimulation is desired for example. A ratio of anode (ring
electrode 537) to blunt dissection electrode surface area should be
selected to support bifocal pacing. In some examples, the anode to
blunt dissection electrode area ratio should be in 2:1 to 30:1,
such as 4:1 to 20:1, such as about 16:1.
Such pacing may be useful to support LV/RV synchronization. For
example, if electrode 535 and blunt dissection electrode 534 are
designed to have a similar pacing capture voltage, the LBB can be
stimulated at the same time as the right septal myocardial (or
right bundle if it were viable and in range of the anode) to
promote LV/RV synchrony. Alternatively, lead 530 may be operated to
provide dual bifocal stimulation. In one example, the dual bifocal
stimulation may operate ring electrode 537 as the anode and
alternatively using blunt dissection electrode 534 and ring
electrode 535 as cathodes. In another example, the dual bifocal
stimulation may operate ring electrode 535 as the anode with and
blunt dissection electrode 534 as the cathode alternated with
operating ring electrode 537 as the anode with and ring electrode
535 as the cathode.
In a variation of lead 530, helix 532 may include an uninsulated
portion forming a helical electrode, such that lead 530 includes
four different electrodes: 534, 535, 532 and 537, each connected to
an individual electrode in the proximal lead connector, which may
conform to the IS-4 standard. For example, cable conductor 533 may
include two insulated conductors, one for each of electrodes 534,
535. In such an example, connection to the proximal connector may
occur by ring or split ring contacts. The four electrodes 534, 535,
532 and 537 may be used in any combination to provide stimulation
and/or sensing. Such flexibility may allow a clinician to adjusting
electrode combinations and/or stimulation parameters to account for
scarring or lead migration, not only at the time of implantation of
such a lead, but also in the months and years following
implantation without the need for surgical intervention.
In further examples, cable conductor 533 may include a plurality of
ring electrodes, such as two to ten electrodes. In such examples,
cable conductor 533 may include a corresponding number of insulated
conductors extending to individual electrical contacts at the
proximal end of cable conductor 533. In one example, the individual
electrical contacts may include ring electrodes, and/or partial
ring electrodes and an optional pin electrode. Including more
electrodes in lead 530 and cable conductor 533 will generally
require a larger lead diameter to account for the additional
conductors. In any of the examples described with respect to lead
530, two or more electrodes may also share a conductor such that
they are operated jointly to provide stimulation or sensing.
A number of modifications to the techniques described herein are
within the spirit of this disclosure. For example, while the
disclosed techniques are described with respect to selecting the
trajectory of an electrode for His bundle pacing, LBB pacing and/or
RBB pacing, the leads and other techniques disclosed herein may
also be used for different target sites, for cardiac pacing and
otherwise.
As another example, the disclosed techniques could be used with any
pulse generator, whether it is in the pectoral pocket or in the
right ventricle. In this manner, the transseptal pacing leads
disclosed herein are suitable with any implantable pulse generator
using any particular pacing programming therapies and/or cardiac
sensing techniques.
Various examples of this disclosure have been described. These and
other examples are within the scope of the following claims.
* * * * *